This invention relates to a blocking device for hand crank drives on automobile sliding roofs, comprising a crank arm, carrying at its end a crank knob and pivotally attached to a rotatable hub plate fixed to the crank pedestal and capable of being folded back over the crank pedestal into a seating slit of the hub plate and locking in a resilient manner in each of its two limiting positions, the crank knob of this crank arm, in a pot-shaped depression of a dish which is non-rotatably fixed concentrically to the crankshaft and surrounds the hub plate.
In the past, hand crank drives for automobile sliding roofs have not been fitted with a braking device or blocking device, so that under the influence of external forces an undesired sliding of the roof panel in the roof opening can occur, for example under the action of high deceleration forces, such as can easily occur when the brakes are fully applied or in an accident. This means that, when the sliding roof is open, the pushed-back panel is accelerated forwards into its closed position. This leads to a risk of injury for the occupants of the vehicle.
The lack of a blocking or braking device is an especially evident nuisance in so-called sliding and lifting roofs. These sliding roofs in which the sliding panel can, as desired, either be swung out by raising its rear edge above the roof surface in the manner of front-pivoted ventilator flaps or can be slid beneath the rear, stationary roof surface. When the sliding panel is swung out, forces acting in the vertical direction, such as can occur for instance in travel vibrations, supplemented by the self-weight of the panel can lead to an unintentional lowering of the rear panel edge.
In one known device (DT-AS No. 1, 219, 342) of the initially mentioned category, a rotational locking for the crank arm is indeed to be achieved in the sunken position by the crank knob entering into the spot-shaped depression, but the sunken position is only reached once during each full crank revolution. Each full crank revolution is equivalent, however, to a considerable longitudinal displacement of the panel, for example of the order of 5 cm. The known device is therefore suitable only for pure sliding roofs, but not for sliding and lifting roofs, because a full pivoting out movement of the panel requires, for instance, only three complete crank revolutions. Moreover, in the known device, the effectiveness of the blocking action is at least partly cancelled by the wall regions of the pot-shaped depression being so inclined that, if a reversed driving motion is transmitted through the panel driving system, the crank knob can easily be expelled from the pot-shaped depression due to the sloping walls, so that the desired blocking action is completely lost. This is, moreover, not prevented by the spring-loaded snap device which determines the limiting positions of the crank arm, because this device is not suitable for accepting the forces which occur when such a reversed driving action takes place.